Contact pieces are used with, for example, low-voltage, medium-voltage and high-voltage switching devices, as well as generator switching devices, which are equipped with vacuum interrupter chambers. The vacuum interrupter chambers are frequently equipped with a so-called radial magnetic field (RMF) contact system. The radial magnetic field is generated by sickle-shaped coil segments. The sickle-shaped elements are produced by slots which are introduced into a contact piece plate. It is also possible to use a slotted contact pot which generates the radial magnetic field on an annular surface.
Any desired slots can be introduced into the contact piece plate. For example, it is also known to use slots in a contact plate when using AMF contact systems. Furthermore, components are produced for widely different applications by powder metallurgy such as when pressing abrasive powders without the use of lubricants.
RMF contact systems can possess low current-path resistance for the overall arrangement using a contact pressure force.
RMF contact pieces in the shape of cylindrical disks are known, whose outer edges are rounded in order to improve the dielectric characteristics. Metal-cutting methods are used to apply the outer contour and to introduce the slots. The external geometry is accordingly applied by a turning operation, and the slots are introduced into the contact piece by sawing or milling. In the case of contact plates which are comparatively thin, it is also possible to use stamping methods. Once the slots have been introduced, the slot edges can be rounded, reworked or deburred manually or by machine in order to increase the dielectric strength of the mutually opposite contact pieces.
Both an external geometry and a slot geometry can be incorporated in a blank directly during production of a contact piece. Slots aligned at right angles to a surface can be introduced as well as slots which are intended to be oriented at an angle to the surface. Furthermore, the slots can extend as far as the external circumference of a disk, and end within it.
Contact pieces are known which are composed of two layers (e.g., CuCr powder layer and Cu powder layer). An erosion-resistant layer may be composed of the standard contact material CuCr 25, which is predominantly used for medium voltages, and a second layer can be composed of pure copper for high conductivity in this layer. Further layers are likewise feasible.
Use of multilayer (e.g., three or more layer) contact blanks and contact pieces is also known.
Furthermore, known methods can be used in engineering for a multiplicity of applications for pressing of powders, such as in the case of abrasive powders. This opens up a wide field for the powder-metallurgical P/M production of components without the use of lubricants, which can be added to the powders to be pressed. These lubricants can be added to the powder materials with a proportion by weight of about 1% in order to considerably lengthen the tool life. However, the lubricants are then forced out of the finally pressed component (the blank).
For example, DE 3840192 C2 discloses a switching contact arrangement for electrical vacuum switches, whose slotted contact pieces are formed from a plurality of disks placed one on top of the other. In this case, the individual disks are slotted by stamping.
U.S. Pat. No. 6,010,659 and EP 1111631 disclose a method for production of a multilayer contact (MLC) having a plurality of layers. An ability to produce a contact from two layers CuCr and copper, for example in a ceramic crucible using the sintering-melting method is also disclosed.
DE 19717024 A1 discloses production of a contact piece provided with slots for a vacuum interrupter chamber, and a shaping tool for carrying out the method. In this case, the slot edges are shaped and are rounded by a pressing process, using a pressing tool.
The slots can also be introduced using metal-cutting methods.
The generation of a contact piece geometry by a cutting technique is, of course, associated with corresponding costs. Manual deburring or deburring by a tool involves an additional process for deburring or rounding of the slot edges.